Furrows for seed and fertilizer placement may be made by pulling a knife through the soil, or by a disc running at an angle to the direction of travel.
Recently double inclined discs have become available for providing furrows for seed and fertilizer, these discs requiring considerably less power to operate than a knife and providing improved penetration over conventional discs. Such a disc is shown in U.S. Pat. No. 5,609,114 to Barton. The disc is inclined from the vertical and toed in from the line of travel with the result that the disc draws itself into the ground. Seed or fertilizer is then introduced into the furrow. The Barton device includes a rear wheel which regulates the depth that the disc goes into the ground and packs the furrow.
As well as particulate seed and fertilizer, gaseous fertilizer, notably anhydrous ammonia, is commonly injected into furrows in soil. It is generally desired to place the gas as deep as possible, in the range of four to five inches, so as to best located for plant use.
Gaseous fertilizers are economical and therefore desirable, however, often the gas escapes from the furrow and is lost to the atmosphere instead of being absorbed into the ground. To combat this escape, the furrow is often packed after injection by a packer wheel passing along the furrow. Such packing however can squeeze the gas out of the soil into the atmosphere where it is lost.
Preferably, the soil around the gas injection location should be fractured and loosened so that the gas is retained in the cavities in loose soil. The furrow should be covered to prevent escape of the gas, but should not be packed, since packing removes the cavities and the gas is forced out of the soil.
The double inclined disc opener is well suited to providing a loose soil as such a disc raises the soil on one side of the disc, fracturing it and thereby providing cavities within the soil. The present packer wheels on such double inclined discs however pack that loose soil, thereby removing the cavities. Such double inclined disc openers also require a means to prevent the soil raised by the inclined disc from being thrown away from the disc as speeds increase. This means usually is a wide rubber wheel running close to the disc.
The knife opener similarly fractures the soil, and present practise is often to leave the furrow open and trust that conditions are such that loosened soil falls back into the furrow to prevent gas escape, or alternatively to pack the furrow, with the result that cavities in the soil are removed. Disc or paddle furrow sealers are also used behind knife openers, as discussed in U.S. Pat. No. 4,596,199 to Dietrich et al.(pages 1 & 2). These have difficulties working in heavy trash conditions such as may be encountered in reduced tillage farming.
Another common problem in agriculture is that while it is necessary to deposit seed into moist soil in order that it germinate and grow, in dry conditions moisture is often several inches under the surface of the soil. Seeding to this depth may allow the seed to germinate, however the plant will have trouble emerging from the surface to gather energy from the sun for further growth. Such deep seeded plants often die before emerging or are excessively weakened by the time they emerge.
Finger wheels have been used in the past to clear residue from the path of a furrow opener to improve penetration and prevent plugging. U.S. Pat. No. 4,785,890 to Martin and U.S. Pat. No. 5,349,911 to Holst et al. show a finger wheel for such an application.
Finger wheels have also been used to close furrows for planters, as disclosed in U.S. Pat. No. 5,497,717 to Martin and in U.S. Pat. No. 5,443,023 to Carroll. These devices comprise at least two finger wheels working together, and are solely addressed to the problem of covering a seed furrow in such way as to improve germination of the seed. They do not address the above problems of (1) retention of gaseous material in the soil, (2) preventing soil from being thrown away from a double inclined disc, (3) removing dry soil from the top of a seed furrow to improve emergence of seed placed deep in the soil in order to be placed in moisture. A single finger wheel, oriented so that the action thereof addresses these problems, would be beneficial.